This invention relates to an apparatus and a method for reading an optical code. More particularly, the invention relates to an apparatus and a method for reading an optical code within a preset distance range.
As is known, optical codes can be read by means of either stationary or portable reading apparatus. In either cases, the apparatus include a casing with a reading window through which a means of illuminating a code to be read, and a means of reading the image of the code being read by detecting light scattered therefrom and converting it to electric signals, are both arranged to act. The detection means for converting the light signal to an electric signal may be of different types; in general, a so-called CCD (Charge-Coupled Device) is used which comprises an array of a very large number of light-sensitive elements.
Reading apparatus of the above-described type have a drawback in that they can only provide a correct reading of the optical codes within a limited distance range; this restricts substantially their applicability.
A problem to be solved in code reading as effected by a human operator and in automatic object sorting and handling systems, is that of identifying and classifying with a single apparatus objects wherein the distance between the reading apparatus and the optical code can considerably vary. In this situation, the use of an apparatus as above described is disadvantageous, since the apparatus is not always capable of correctly focusing on the object codes to be identificated.
The underlying technical problem of this invention is that of enabling proper reading of optical codes placed at varying distances within a broad range of distances, using an apparatus of simple and low-cost construction.